The present invention relates to the protection of the contents of an enclosed space, especially people, against damage caused by flying debris when the walls of the enclosed space are destroyed and the window frames which are no longer secured thereby are ejected inwardly into the interior of the enclosed space.
Bomb blasts are unfortunately a relatively common occurrence, whether in the context of actual warfare or otherwise. Little can be done to prevent damage to persons and objects who suffer a direct hit from the blast.
However, a significant fraction of the persons and property which are hurt or damaged during a bomb blast do not suffer a direct hit and rather are separated from the detonation by a structure. Typically, the persons or objects are inside a house or building while the blast takes place outside the house or building.
It is known that in the case where a blast occurs outside of a structure, some of the damage caused to persons and objects inside the structure are brought about by flying pieces of the walls of the structure as they are broken up and thrust inward by the force of the explosion.
In many cases, a substantial portion of the damage is caused by window frames which are no longer secured by the disintegrating walls of the structure and are forced inwardly by the blast, hurting people and inflicting damage to property. For example, more than 90% of those killed and wounded in the recent blast of the American embassy building in Nairobi were hurt by window frames that were forcibly ejected from the walls and thrown into the rooms of the building, although the window glass in the American embassy in Nairobi were re-enforced with Mylar film coating.
An obvious solution to the problem is to build structures which have strong walls and window frame installations which are capable of withstanding the forces of any expected blast without breaking up. Such walls can be made to be sufficiently strong by increasing the thickness of the wall, reinforcing the wall, or making the wall from a stronger material, carrying blast proof window frames.
Such a solution is not always practicable. Use of blast-proof walls and window frames is expensive and, while certain blast-prone structures may feature such walls and frames, it is not feasible to equip every structure which is the potential target of a bomb blast with such walls and frames.
Retrofit attempts to reinforce existing walls with a reinforcing and protection structure have employed thermosetting adhesive between the reinforcing structure and the wall. Thermosetting adhesives by nature become rigid when cured, thus precluding the very properties of stretch and hold required for the reinforcing structure to perform effectively as a protective shield.
There is thus a widely recognized need for, and it would be highly advantageous to have, a means for protecting the contents of a structure, especially human beings, from harm which may be caused when a blast outside the structure breaks up the walls of the structure and forcibly sends pieces of the walls and the window frames into the structure.